Some callers use Chain Thru from formations such as
Parallel Lines and want all the Centers to Trade; and all to
Cast Off 3/4.
We believe this is an invalid usage of Chain Thru since it can be
ambiguous in several situations. For example, from a Tidal Wave, does
the caller want the Very Centers to Trade & then the Center 4 to Cast
Off 3/4, or does the caller want each side to do a Centers
Trade & all Cast Off 3/4? Also, if Chain Thru is
allowed to mean each side Centers Trade followed by all Cast Off 3/4,
then from Twin Diamonds a Chain Thru could be
interpreted as Centers of each Diamond Trade (since they are Centers
of their 4-dancer formation), followed by confusion, since there is no
adjacent dancer within their 4-dancer formation with whom to Cast Off 3/4.